this is from permies.com:
Related to the word 'glaze', a gley is like a biological plastic membrane such as is found in bogs, which is formed by a bacterial process that requires anaerobic conditions.
Traditionally a technique for sealing ponds and dams, there is potential for the process to be adapted for human-made structures. The Russian-devised version for dams uses a slurry of animal waste (pig manure) applied over the inner base and walls of the dam in multiple, thin layers, which is then itself covered with vegetable organic matter such as grass, leaves, waste paper, cardboard, etc. This is all then given a final layer of soil which is tamped down and the mixture is left for several weeks to allow the (anaerobic) bacteria to complete their task, at which time the dam is ready for flooding.
Gleys have the potential to revolutionise water storage capacity in regions with hightly porous soils. An aquaculture industry in otherwise unsuitable areas scould be one of the benefits of this technique.
Unlike bentonite clay, gley materials are virtually cost-free and are comprised of 'wastes' which would normally be discarded in the normal course of operations. Also, plastic and rubber dam liners may actually be dependent on the same anaerobic process for their own continued effectiveness rather than their lack of holes or punctures * ie, it is the anaerobic layer created below them rather than their own membranous qualities which prevent water seepage in the long term. "
Where I live they use bentonite clay. Carpets are really full of disgusting chemicals, and I'm not sure I'd want to line a pond with them.
"Life flows on within you and without you"...George Harrison
Coastal California, USA, Mediterranean climate - no summer rain, a little frost mid-winter